Means to prevent gumming and sticking of automatic choke mechanism



Nov. 15, 1966 G. F. ROSBROOK 3,285,279

MEANS To PREVENT GUMMING AND STICKING OF AUTOMATIC CHOKE MECHANISM Filed Nov. 19, 1963 T INVENTOR. MAN/FOLD Z 5 Q'ffbra .ffiasrow VACUUM BY United States Patent of Delaware Filed Nov. 19, 1963, Ser. No. 324,705 3 Claims. (Cl. 137-483) This invention relates to means to prevent gasoline and oil vapors from passing from an internal combustion engine air induction passage to the automatic choke mechanism.

The automatic choke mechanism often tends to stick and become inoperative because of the contaminant in gasoline and oil vapors being deposited on the shaft and other parts of the choke mechanism. This problem has existed for many years but it has become more severe due to the increased use of crankcase cycling systems in which crankcase fumes are taken into the carburetor.

This invention prevents the contaminants from depositing on the choke shaft and choke mechanism by drawing gasoline and oil vapors to the engine intake manifold. Any vapors present in the choke housing are also drawn to the intake manifold.

The objects and advantages of this invention will become apparent from the following specification and drawings wherein:

FIGURE 1 is an elevational view of a carburetor partly broken away to show the automatic choke mechanism in which the present invention is incorporated;

FIGURE 2 is an enlarged view of the automatic choke portion of FIGURE 1; and

FIGURE 3 is a view taken substantially along the line 33 of FIGURE 2, with portions broken away, to show the details of the automatic choke.

Since this invention is concerned solely with the automatic choke mechanism and the shaft for connecting it to the choke valve the details of the carburetor are neither shown nor described. Generally, as shown in FIGURE 1, the carburetor includes an induction passage 12. Rotatably disposed within this passage is a choke valve 14 which is connected by means of a shaft 16 to the automatic choke mechanism designated generally 18. A housing 20 and cover 22 form the enclosure for the automatic choke mechanism. The shaft 16 is journaled in passage 23 which connects the induction passage 12 with the housing 20. The choke mechanism includes a coiled metallic thermostat 24 which is connected to the choke shaft 16 through a choke lever 26 secured to the shaft. The thermostat 24 is fixedly connected in any suitable way to a pin 28 which is secured to the cover plate 22. A piston 30 is slidably disposed within cylinder 32 and is connected to choke lever 26 through link 34.

Engine vacuum is communicated to the cylinder 32 by means of a conduit 36 and because of an imperfect fit of the piston 30 in the cylinder 32 the pressure in housing 20 is normally subatmospheric. Gasoline and oil vapors in induction passage 12 will thus tend to flow through the passage 23 into the housing 20 and the contaminants in the vapors will tend to deposit on the shaft 16 and other parts of the automatic choke mechanism causing them to stick and become inoperative.

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This invention reduces the tendency of vapors to flow into the choke housing by providing a by-pass passage 38 which connects an intermediate portion of the passage 23 with the intake manifold. Because of the reduced pressure in by-pass passage 38 due to manifold vacuum, gasoline and oil vapors which flow in the passage 23 along choke shaft 16 from the intake manifold 12 will be bypassed through passage 38 to the engine manifold. Vapors present in the choke housing 20 will also be drawn to the intake manifold through passage 38.

What is claimed is:

1. An automatic choke mechanism for an internal combustion engine having a wall defining an air induction passage, said choke mechanism including a housing mounted on said wall exterior of said passage and enclosed by a portion of said wall, a shaft journal passage in said portion of said wall extending from said housing to said induction passage, a shaft journaled in said journal passage, a choke valve disposed in said induction passage and secured to said shaft for rotational movement therewith, choke operating mechanism disposed within said housing and including a piston disposed in a cylinder, said piston being operatively connected to said shaft, means connecting said cylinder to a source of engine vacuum for operating said piston and shaft, said piston being loosely disposed in said cylinder whereby said housing is subjected to subatmospheri c pressures tending to create a potential for fluid flow along said shaft from said induction passage to said housing, and means reducing said potential comprising a =by-pass passage extending from an intermediate portion of said journal passage, said =by-pass passage being connected to a source of vacuum whereby a potential for fluid flow along said shaft is created from said induction passage only to said by-pass passage.

2. The automatic choke mechanism of claim 1 wherein said source of vacuum for said by-pass passage is a source of engine vacuum.

3. The automatic choke mechanism of claim 2 which further includes a common passage extending from said induction passage at a point thereof maintained at su-batmospheric pressure, said common passage having a first branch forming said by-pass passage and a second branch connected to said cylinder.

References Cited by the Examiner UNITED STATES PATENTS 1,982,071 11/1934 Roberts 251119 2,265,676 12/1941. Stoddard 222152 X 2,635,903 4/1953 Hansen 251-214 X 2,766,768 10/1956 Brown et al. 251-214 X 2,848,201 8/1958 Bennett 123-119 FOREIGN PATENTS 652,764 10/1928 France. 751,891 7/1933 France.

OTHER REFERENCES Vacuum Equipment and Techniques, Guthrie, A. and Wakerling, R. K., McGraw Hill, 1949, pp. 154, and 166.

M. CARY NELSON, Primary Examiner.

S. SCOTT, Assistant Examiner. 

1. AN AUTOMATIC CHOKE MECHANISM FOR AN INTERNAL COMBUSTION ENGINE HAVING A WALL DEFINING AN AIR INDUCTION PASSAGE, SAID CHOKE MECHANISM INCLUDING A HOUSING MOUNTED ON SAID WALL EXTERIOR OF SAID PASSAGE AND ENCLOSED BY A PORTION OF SAID WALL, A SHAFT JOURNAL PASSAGE IN SAID PORTION OF SAID WALL EXTENDING FROM SAID HOUSING TO SAID INDUCTION PASSAGE, A SHAFT JOURNALED IN SAID JOURNAL PASSAGE, A CHOKE VALVE DISPOSED IN SAID INDUCTION PASSAGE AND SECURED TO SAID SHAFT FOR ROTATIONAL MOVEMENT THEREWITH, CHOKE OPERATING MECHANISM DISPOSED WITHIN SAID HOUSING AND INCLUDING A PISTON DISPOSED IN A CYLINDER, SAID PISTON BEING OPERATIVELY CONNECTED TO SAID SHAFT, MEANS CONNECTING SAID CYLINDER TO A SOURCE OF ENGINE VACUUM FOR OPERATING SAID PISTON AND SHAFT, SAID PISTON BEING LOOSELY DISPOSED IN SAID CYLINDER WHEREBY SAID HOUSING IS SUBJECTEDD TO SUBATMOSPHERIC PRESSURES TENDING TO CREATE A POTENTIAL FOR FLUID FLOW ALONG SAID SHAFT FROM SAID INDUCTION PAS SAGE TO SAID HOUSING, AND MEANS REDUCING SAID POTENTIAL COMPRISING A BY-PASS PASSAGE EXTENDING FROM AN INTERMEDIATE PORTION OF SAID JOURNAL PASSAGE, SAID BY-PASS PASSAGE BEING CONNECTED TO A SOURCE OF VACUUM WHEREBY A POTENTIAL FOR FLUID FLOW ALONG SAID SHAFT IS CREATED FROM SAID INDUCTION PASSAGE ONLY TO SAID BY-PASS PASSAGE. 